Human G-CSF Quantikine ELISA Kit Summary

Product Summary

The Quantikine Human G-CSF Immunoassay is a 3.5 or 4.5 hour solid phase ELISA designed to measure G-CSF in cell culture supernates, serum, and plasma. It contains E. coli-expressed recombinant human G-CSF and antibodies raised against the protein. It has been shown to accurately quantitate recombinant human G-CSF. Results obtained using natural human G-CSF showed linear curves that were parallel to the standard curves obtained using the Quantikine kit standards. These results indicate that this kit can be used to determine relative mass values for natural human G-CSF.

Preparation and Storage

Background: G-CSF

Granulocyte-colony stimulating factor (G-CSF) is a 24-25 kDa monomeric glycoprotein that regulates the proliferation, differentiation, and activation of hematopoietic cells in the neutrophilic granulocyte lineage. Mature human G-CSF is a 178 amino acid (aa) O-glycosylated protein that contains two intrachain disulfide bridges. In humans, alternate splicing generates a second minor isoform with a 3 aa deletion. Mouse and human G-CSF share 76% aa sequence identity, and the two proteins show species cross-reactivity. G-CSF is produced by activated monocytes and macrophages, fibroblasts, endothelial cells, astrocytes, neurons, and bone marrow stroma cells. In addition, various tumor cells express G-CSF constitutively.   

Human G-CSF receptor (G-CSF R) is a 120 kDa type I transmembrane glycoprotein that belongs to the hematopoietin receptor superfamily. The mature protein consists of a 603 aa extracellular domain (ECD), a 23 aa transmembrane segment, and a 186 aa cytoplasmic domain. The ECD contains an N-terminal Ig-like domain, a cytokine receptor homology domain, and three fibronectin type III domains. Alternate splicing of human G-CSF R generates additional isoforms including a potentially soluble form of the receptor. The ECDs of mouse and human G-CSF R share 63% aa sequence identity. G-CSF R forms a complex with the ligand in a 2:2 ratio. It is expressed on monocytes, neutrophils, megakaryocytes, platelets, myeloid progenitors, trophoblasts and placenta, endothelial cells, and various tumor cell types.   

G-CSF is an important regulator for granulopoiesis in vivo, and mutations in G-CSF R are associated with congenital neutropenia. G-CSF can support the growth of multilineage hematopoietic progenitor cells and mobilize them from the bone marrow into the bloodstream. G-CSF enhances the functional capacity of mature neutrophils and supports their survival by limiting the rate of apoptosis. G-CSF also enhances M-CSF induced monocytopoiesis from hematopoietic progenitor cells and stimulates the proliferation of peripheral Th2-inducing dendritic cells (30, 31). It promotes the development of T cell immune tolerance as well as tissue recovery following myocardial infarction and cerebral ischemia.

Assay Procedure

Refer to the product datasheet for the complete assay procedure.

Bring all reagents and samples to room temperature before use. It is recommended that all samples, standards, and controls be assayed in duplicate.

1.     Prepare all reagents, standard dilutions, and samples as directed in the product insert.

2.     Remove excess microplate strips from the plate frame, return them to the foil pouch containing the desiccant pack, and reseal.

3.     Add 50 μL of Assay Diluent to each well.

4.     Add 50 μL of Standard, control, or sample to each well. Cover with a plate sealer, and incubate at room temperature for 2 hours.

5.     Aspirate each well and wash, repeating the process 4 times for a total of 5 washes.

6.     Add 100 μL of Conjugate to each well. Cover with a new plate sealer, and incubate at room temperature for 2 hours.

7.     Aspirate and wash 5 times.

8.     Add 100 μL Substrate Solution to each well.

9.     Add 100 μL of Stop Solution to each well. Read at 450 nm within 30 minutes. Set wavelength correction to 540 nm or 570 nm.